A team of researchers has discovered a previously unknown biological pathway that appears to play a key role in how certain hairs trigger itching sensations.
In new, published this month in Neuronscientists identified, in rats, a new sensory pathway that links touch-sensitive hair to the desire to scratch. A type of hair that had previously been little studied was also described, the hair veilas well as a set of sensory neurons responsible for detecting its movement and transmitting itching signals to the nervous system.
According to , researchers analyzed mice with chronic skin inflammation, similar to human eczema. They found that animals with these active neurons displayed normal scratching behavior. Rats without these neurons, or with them deactivated, scratched much less, indicating that this pathway is essential for the so-called mechanical itching.
Although this study was carried out in mice, humans have the genes needed to produce similar neurons.
“Our study indicates that humans may have this same type of mechanism to transmit itching and also reveals that the body has a specific system for this type of sensation,” said the study’s lead author, Bo Duan.
Scientists have also identified proteins involved in transmitting these signals to the spinal cord. When tested on cultured human neurons, these proteins caused similar answerssuggesting that this mechanism may also exist in humans.
To investigate this phenomenon, the team developed a new experimental method. They gently stimulated the mice’s hair with a small loop of wire and observed their reactions.
Afterwards, genetically modified the neurons so they could be activated by blue light. When stimulated in this way, the rats scratched as if they had been touched, confirming the direct role of these neurons.
Although vellus hair covers a large part of the body, the spinal cord has circuits that filter these stimuli, preventing common sensations, such as the brush of clothing or a light breeze, from causing constant itching.
Ultimately, researchers believe that this system may have evolved as a defense mechanism and that their discovery could pave the way for new treatments for chronic itch diseases.
